Although boys with attention-deficit hyperactivity disorder (ADHD) are at risk for persistent symptomatology and negative outcomes in adolescence and adulthood, there is almost no information on the prospective follow-up of girls with ADHD. Furthermore, data on the developmental course of the Inattentive type of ADHD (which is of particular salience for females) are almost nonexistent. The key purpose of the proposed continuation is to follow prospectively a diverse and well-characterized sample of preadolescent girls with ADHD plus a matched comparison group. The PI has gathered a comprehensive database on this sample, which includes state-of-the-art clinical assessment plus multi-domain/multi-informant information from naturalistic research settings. Subjects are on 140 ethnically diverse girls with ADHD (both Combined and Inattentive types) and 88 comparison girls, all of whom were 6-12 years of age during baseline assessment. The initial database spans key domains (ADHD symptomatology; disruptive and internalizing comorbidity; functional impairment in home, school, and peer settings; cognitive and neuropsychological performance), reflects unmedicated behavior, and features ecologically valid observational and peer sociometric data collected during summer research programs. The proposed research incorporates comprehensive, 4-year, prospective follow-up (at ages 11-16.5 years), across multiple domains of symptoms, impairment, and competence. A key aim is to describe change and stability across the period from childhood to adolescence in girls with ADHD. Another is to build predictive and explanatory models that test the salience of behavioral, cognitive, and environmental factors in explaining persistence and desistance from ADHD-related symptomatology and comorbidity. A third features the testing of risk/resiliency models in explaining competencies at follow up. Featured are (a) contrasts of Combined- vs. Inattentive-type ADHD and (b) person-centered approaches to appraising developmental mechanisms. Overall, prospective follow-up is necessary to evaluate processes and mechanisms underlying both stability and discontinuity in the understudied population of females with ADHD. The proposed research features a large and well-characterized sample plus conceptually sound and developmentally based assessment procedures.